1. Field of the Invention
This disclosure relates to a method for brightness control and, more particularly, to a method for brightness control, which is adapted to a light emitting device, capable of improving user experience, and having flexibility on system design.
2. Description of Related Art
FIG. 1 shows a waveform of brightness of a light emitting device controlled by prior arts. The initial value of the output brightness of the light emitting device is 0%, and the target value of that is set to be 100%. In FIG. 1, the waveforms, which are waveform 110 and 120, respectively corresponding to 2 different prior arts are shown. Waveform 110 shows that the output brightness is linearly changed from the initial 0% to target 100%, which is easier for system design and the required time to finish the change on the output brightness can be clearly estimated. However, the brightness changing rate is the same both for smaller brightness and larger brightness, which is not gentle for users and may cause uncomfortable visual feeling.
On the other hand, waveform 120 shows that the output brightness is exponentially changed, which takes advantage of relatively easier design on the control circuit of the light emitting device, such as a circuit formed by serially connecting resistors and capacitors. The exponentially changing brightness is relatively gentle for users and shows obvious gradation on brightness. By this way the user experience is improved comparing to the prior art shown by waveform 110. However, the changing time of the exponentially changing brightness is either not easy to be possessed or too long, which causes inconvenience on system design.